This invention relates generally to hand-held aerosol spray devices, and more particularly to devices of this type employing an inner collapsible bag containing substance to be discharged and a can or outer casing constituting a housing, wherein a spring disposed in the casing is employed to press against a wall portion of the bag and thus pressurize the same. Such a device is disclosed in U.S. Pat. No. 3,335,913, and employs a spring-biased bellows, a valve communicating therewith and a discharge button or actuator. In this construction, the compressive force exerted by the spring on the bellows is greatest when the dispenser is full. As the contents are gradually exhausted, the spring expands causing successively greater collapse of the bag. Under such circumstances, the force exerted by the spring is reduced considerably as the bag contents become depleted. This leads to a reduction in pressure in the bag, resulting in a lower velocity spray discharge through the valve. It has been found that such a reduction in pressure is objectionable in that the characteristics of the spray depend largely upon the degree of depletion of the container contents. Attempts to alter the spring compression for satisfactory performance at either the full or the empty condition of the dispenser have represented at best a compromise solution to the above problem. In addition, in many prior constructions employing bellows-type flexible containers, it has not been possible to dispense the last portion of substance, since the bellows could undergo only limited compression. As a result, there was almost always some residual liquid which could not be dispensed and which was thus wasted when the dispenser was discarded.